diff --git a/checker/default/int.go b/checker/default/int.go
new file mode 100644
index 0000000..2e811cf
--- /dev/null
+++ b/checker/default/int.go
@@ -0,0 +1,12 @@
+package main
+
+func Match(name string) bool {
+	return name == "int"
+}
+
+func Check(value interface{}) bool {
+	_, intOK := value.(int)
+	_, uintOK := value.(uint)
+
+	return intOK || uintOK
+}
diff --git a/checker/default/string.go b/checker/default/string.go
new file mode 100644
index 0000000..57796e5
--- /dev/null
+++ b/checker/default/string.go
@@ -0,0 +1,11 @@
+package main
+
+func Match(name string) bool {
+	return name == "string"
+}
+
+func Check(value interface{}) bool {
+	_, OK := value.(string)
+
+	return OK
+}
diff --git a/checker/default/varchar.go b/checker/default/varchar.go
new file mode 100644
index 0000000..fad7223
--- /dev/null
+++ b/checker/default/varchar.go
@@ -0,0 +1,73 @@
+package main
+
+import (
+	"regexp"
+	"strconv"
+)
+
+var min *uint64 = nil
+var max *uint64 = nil
+
+func Match(name string) bool {
+
+	/* (1) Create regexp */
+	re, err := regexp.Compile(`^varchar\((\d+), ?(\d+)\)$`)
+	if err != nil {
+		panic(err)
+	}
+
+	/* (2) Check if matches */
+	matches := re.FindStringSubmatch(name)
+	if matches == nil || len(matches) < 3 {
+		return false
+	}
+
+	/* (3) Extract min */
+	minVal, err := strconv.ParseUint(matches[1], 10, 64)
+	if err != nil {
+		return false
+	}
+	min = &minVal
+
+	/* (4) Extract max */
+	maxVal, err := strconv.ParseUint(matches[2], 10, 64)
+	if err != nil {
+		return false
+	}
+
+	/* (5) Check that min <= max */
+	if maxVal < minVal {
+		panic("varchar(x, y) ; constraint violation : x <= y")
+	}
+	max = &maxVal
+
+	return true
+
+}
+
+func Check(value interface{}) bool {
+
+	/* (1) Check if string */
+	strval, ok := value.(string)
+	if !ok {
+		return false
+	}
+
+	/* (2) Check if sizes set */
+	if min == nil || max == nil {
+		return false
+	}
+
+	/* (3) Check min */
+	if uint64(len(strval)) < *min {
+		return false
+	}
+
+	/* (4) Check max */
+	if uint64(len(strval)) > *max {
+		return false
+	}
+
+	return true
+
+}
diff --git a/checker/public.go b/checker/public.go
index 2d2a3fb..699fa18 100644
--- a/checker/public.go
+++ b/checker/public.go
@@ -8,7 +8,7 @@ import (
 
 // CreateRegistry creates an empty type registry
 // if TRUE is given, it will use default Types
-// see ./default_types.go
+// see ./default/ folder
 func CreateRegistry(useDefaultTypes bool) *TypeRegistry {
 	return &TypeRegistry{
 		Types: make([]Type, 0),
@@ -67,7 +67,7 @@ func (tr *TypeRegistry) Add(pluginName string) error {
 }
 
 // Checks the 'value' which must be of type 'name'
-func (tr TypeRegistry) Run(name string, value interface{}) bool {
+func (tr TypeRegistry) Run(name string, value interface{}) error {
 
 	var T *Type = nil
 
@@ -79,18 +79,18 @@ func (tr TypeRegistry) Run(name string, value interface{}) bool {
 			T = &t
 			break
 		}
-
-		// else log
-		fmt.Printf("does not match\n")
 	}
 
 	/* (2) Abort if no matching type */
 	if T == nil {
-		return false
+		return fmt.Errorf("No matching type")
 	}
 
 	/* (3) Check */
-	fmt.Printf("Check is %t\n", T.Check(value))
-	return T.Check(value)
+	if !T.Check(value) {
+		return fmt.Errorf("Does not match")
+	}
+
+	return nil
 
 }